Open Loop Power Control (OLPC) Measurement

Last updated: 2014-11-28

Open Loop Power Control Measurement Description

As defined in the 3GPP standard TS 34.122 5.4.1.3, the open loop power control is the ability of the UE transmitter to sets its output power to a specific value.

The open loop power control measurement can only be initiated when the Operating Mode is Active Cell and the call status is Idle.

In Active Cell operating mode, when the open loop power control measurement is initiated, the test set captures the first UpPTS burst in an access sequence, and measures the RRC filtered mean power in UpPTS timeslot.

During this measurement, the Call Limit State is locked to On by the test set to prevent the call status from transiting to Connected. Besides, if the Power Control is set to Auto, changing the Cell Power, Broadcast Primary CCPCH Tx Power or the Desired UpPCH RX power will lead the expected input power level of the test set to be changed, which will accordingly cause the measurement to be aborted.

The Open Loop Power Control Measurement can not be performed in concurrence with other measurements.

The open loop power control measurement can only be initiated when the Operating Mode is Active Cell and the call status is Idle.
Before the open loop power control measurement, the UE must be informed of the following updated parameters from the downlink BCH: Broadcast Primary CCPCH Tx Power, UpPCH Power Ramp Step, Desired UpPCH RX power and Max Sync UL Transmissions etc. This can be archived by performing a registration or call origination beforehand.
The open loop power control measurement can only be initiated with the Trigger Arm to be Single.

Open Loop Power Control Measurement Parameters

Initial UpPCH Tx Power Limit: this parameter is expressed in dB and specifies the open loop power control tolerance. The difference between the measurement result and the expected power should be less than this limit.

GPIB Command: SETup:TOLPower:LIMit

Measurement Timeout: see Measurement Timeout.

GPIB Command: SETup:TOLPower:TIMeout[:STIMe]

Open Loop Power Control Measurement Results

You can fetch all the OLPC results all together by a single GPIB command: FETCh:TOLPower[:ALL]?

Initial UpPCH Tx Power Measurement Results: the RRC filtered mean power in UpPTS slot.

GPIB Command: FETCh:TOLPower:POWer? and FETCh:TOLPower:FAIL?

Detected UpPCH Signature

GPIB Command: FETCh:TOLPower:SIGNature?

Input Signal Requirements

The measured signal level is expected to be within +10 dB to -20 dB of the expected power.
Input level is between -60 dBm and +28 dBm.
Frequency is within 20KHz from the expected measurement receiver frequency.

How Do I Make an Open Loop Power Control Measurement?

The following procedure performs the 3GPP TS 34.122 5.4.1.3 Open loop power control (1,28 Mcps TDD Option), as an example.

Initial conditions

Connect the UE to the front panel RF IN/OUT port.
Set call parameters as following (RX-middle parameters in 3GPP TS 34.122 Table 5.4.1.3.4b):

[F7 in Call Parms 1 of 3] Set the Cell Power to -66 dBm.
[F12 in Call Parms 1 of 3] In UE Transmit Pwr Control, set as the following:
Set the Broadcast Primary CCPCH Tx Power to +24 dBm (default value).
Set the Desired UpPCH RX Power to -100 dBm (default value).
Set the UpPCH Power Ramp Step to 0 dB.

Set call control parameters as following:
[F5 in Call Control 2 of 3] In Channel Config Info, press F1 (Uplink Channel Config), set the Max SYNC UL Transmissions to 1.

[F7 in Call Parms 3 of 3] Set the MS DPCH Tgt Pwr to -10 (default value).

Procedure

Press the Measurement selection key.
Select Open Loop Power.
Select Open Loop Power Setup (F1). Set the measurement parameters as needed for your measurement situation, such as the Initial UpPCH Tx Power Limit.
Press the START SINGLE key to begin the measurement. An example measurement result is shown as below: